The present invention relates generally to new and novel improvements in a splice joint for plastic coated fabric conveyor belt and method of making the same. More particularly, the present invention relates to a splice joint for plastic coated fabric conveyor belt and method of making the same which is particularly suitable for use in machines which fabricate metal can lids.
Machines which fabricate metal can lids typically include a continuous conveyor belt to transport and position the metal can lid material during the metal can lid fabrication process. While it would be beneficial to utilize an endless conveyor belt for the continuous conveyor belt in such metal can lid fabricating machines, the design of most metal can lid fabricating machines precludes the use of an endless conveyor belt. In particular, most metal can lid fabricating machines require a conveyor belt to be threaded through the metal can lid fabricating machine around pulleys therein and the two (2) free conveyor belt ends are then brought together and joined together to form a spliced continuous conveyor belt.
Spliced continuous conveyor belts used in metal can lid fabricating machines are sometimes fabricated by joining the two (2) free conveyor belt ends with a straight butt splice joint, often cut at an angle to increase the surface area of the splice joint. Another known prior art method of joining the two (2) free conveyor belt ends involves cutting the two (2) free conveyor belt ends into a configuration commonly referred to as a "finger" type splice. In this configuration, the two (2) conveyor belt ends are typically overlapped and sheared or cut in a matched wavy or "finger" pattern. Such a "finger" type splice can be seen in U.S. Pat. No. 5,342,250 to Sanders for a "Process for the Manufacture of an Endless Transfer Belt." After shearing or cutting the two (2) conveyor belt ends into a matched wavy or "finger" pattern, the conveyor belt is threaded through the metal can lid fabricating machine and the two (2) conveyor belt ends are abutted together and melted to form a continuous spliced conveyor belt. Pre-cut holes or pockets in the conveyor belt transport the metal can lid materials through the metal can lid fabricating machines through various forming operations to fabricate metal can lids having the desired configuration.
Conveyor belts used in metal can lid fabricating machines are often subjected to high levels of tension and stress due to the high speeds at which conveyor belts are driven around the pulleys in typical metal can lid fabricating machines. This may cause conventional spliced continuous conveyor belts to tear, stretch or separate in the vicinity of the splice during normal operating conditions. Since most metal can lid fabricating machines require precise positioning of the metal can lid materials to fabricate metal can lids having the desired configuration, any deviation in the length of the spliced continuous conveyor belt could be detrimental to the metal can lid fabricating process.
In addition, vulcanizing units used to heat known prior art conveyor belts used in metal can lid fabricating machines have a broader than desired heating zone. Such vulcanizing units are generally multi-purpose units and are not designed for spliced continuous conveyor belts having lengths which are fabricated to close dimensional tolerances. Such a broad heating zone tends to deform the conveyor belt and affect the positioning of precision cut drive holes which are pre-punched into the conveyor belt. Deformation of these areas can result in misalignment of the metal can lid materials in the forming process and significantly reduce the service life expectancy of the conveyor belt. Thus, it is generally desirable to position the splice between the "holed" areas of the conveyor belt to shield the drive holes from heat from the vulcanizer unit.
In the shearing or cutting process used to fabricate spliced continuous conveyor belts for metal can lid fabricating machines, a pair of sharp shearing or cutting blades, including an upper shearing or cutting blade and a lower shearing or cutting blade, are brought into close proximity to one another. The conveyor belting material that is positioned between the shearing or cutting blades is sheared or cut by the combination of the force applied by the shearing or cutting blades, the hardness of the shearing or cutting blades and the sharpness of the shearing or cutting blade edges. If more than one (1) layer of material lies between the shearing or cutting blades and the upper shearing or cutting blade is brought down towards the lower shearing or cutting blade, the bottom layer of the material becomes the lower shearing plane for the upper layer of material. Since the lower layer of material does not have the hardness and sharpness characteristics of a shearing or cutting blade, it will tend to compress, flow and distort the cut edges of both the upper and the lower material layers.
Vulcanization is a term used to describe the process of joining rubber and/or plastic materials together by heating the materials under an applied pressure in a confined environment to cause the particles in the materials being joined to flow and intermix with each other. As the temperature is reduced, the materials cool and the particles cure together to form a solid bond. In utilizing this process to fabricate a continuous spliced conveyor belt having a straight butt splice joint or a "finger" type splice joint, the wavy or "finger" conveyor belt ends tend to draw away from each other due to the pressure applied during the vulcanization process. This drawing away of the conveyor belt ends can result in less than desirable intermixing of the particles during the vulcanization process, thus forming a joint which is weaker than desirable.
Accordingly, an object of the present invention is the provision of a splice joint for plastic coated fabric conveyor belt or similar article which provides an initial mechanical bond between the two (2) conveyor belt ends to preclude movement or withdrawal of the (2) conveyor belt ends relative to each other during the vulcanization process.
Another object of the present invention is the provision of a splice joint for plastic coated fabric conveyor belt or similar article which utilizes a relatively narrow heat zone to vulcanize the two (2) conveyor belt ends to be joined together and shields the remainder of the conveyor belt from the heat used in the vulcanizing process.
A further object of the present invention is the provision of a splice joint for plastic coated fabric conveyor belt or similar article which provides increased surface area on the two (2) conveyor belt ends in the splice joint zone to provide a stronger bond between the two (2) conveyor belt ends.
Yet another object of the present invention is the provision of a splice joint for plastic coated fabric conveyor belt or similar article which provides for a stronger and more durable splice between the two (2) conveyor belt ends.
Yet a further object of the present invention is the provision of a splice joint for plastic coated fabric conveyor belt or similar article which provides better dimensional accuracy for a continuous spliced conveyor belt fabricated by joining two (2) conveyor belt ends.
These and other objects of the present invention are attained by a splice joint for plastic coated fabric conveyor belt or similar article which initially provides a mechanical bond between the two (2) conveyor belt ends to be joined prior to a vulcanization process. This is achieved by providing a "jig-saw puzzle" type splice joint between the two (2) conveyor belt ends to be joined wherein at least one of the conveyor belt ends to be joined has outwardly extending mushroom shaped tabs and/or outwardly extending arrow-head shaped tabs and the other conveyor belt end to be joined has corresponding inwardly extending sockets to provide both increased splice joint surface area, as well as a mechanical bond, between the two (2) conveyor belt ends to be joined.